Over the past few decades, there has been interest in chalcogenide materials for use in semiconductor devices, such as non-volatile memories, solar cells, photodetectors, or electroconductive electrodes. For example, chalcogenide materials have been used in phase change random access memory devices. Chalcogenide materials are capable of stably transitioning between physical states (e.g., amorphous, semi-amorphous, and crystalline states) upon the application of a physical signal (e.g., a high current pulse, or a low current pulse). Each physical state can exhibit a particular resistance that may be used to distinguish logic values of a phase change memory random access memory cell.
One of the current difficulties associated with the use of chalcogenide materials in semiconductor device structures is the formation of the material. Chalcogenide materials have been formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). PVD and CVD processes lack the conformality needed to uniformly deposit material on a substrate, as integrated circuit scaling approaches less than or equal to 10 nanometers (nm). In addition, due to the equipment and targets needed, PVD processes can be expensive. ALD processes have been used to form chalcogenide materials by reacting alkyl tellurides and alkyl selenides with volatile, pyrophoric, alkyl reactants to form metal tellurides or metal selenides. For example, alkyl tellurides have been reacted with dimethylcadmium to form cadium telluride through ALD processes. However, ALD processes for forming chalcogenide materials are limited by the availability (e.g., volatile alkyl compounds suitable for reaction with tellurium compounds in ALD processes do not exist for many for many metals), reactivity, and toxicity of appropriate ALD precursors.
It would be desirable to be able to form additional chalcogenide materials using ALD processes. It would be further desirable if chalcogenide materials formed using the ALD processes exhibited high purity, and if any precursors used in the formation of the chalcogenide materials were readily available, less toxic, and non-pyrophoric.